This invention relates generally to distributed data processing systems and more particularly to the control of communication between components of such systems.
Access to distributed data processing systems is conventionally obtained by tokens such as plastic cards carrying data in the form of magnetic stripes. Increasingly, active tokens, referred to as smart cards, incorporating data processing and storage facilities, are being used to provide access to more sophisticated facilities such as customer loyalty programs.
Smart cards have been used in various applications including retailing, automatic teller machines (ATM""s) and the control of access to pay TV facilities. As the use of such cards increases so does the need for communicating data in a manner appropriate to the transaction. For example, in a retail system using a number of customer transaction tills linked to one or more servers for processing transactions controlled by smart cards it is highly desirable that each smart card application seeking to communicate with a server is connected to a logical data xe2x80x9cpipexe2x80x9d which delivers all the data connected with the transaction efficiently and with an appropriate degree of security. In practice it is necessary to use communication links which are already established within a network, which may not be ideally suited to a given application.
In accordance with the present invention there is provided a distributed data processing system comprising one or more processing terminals arranged for communication over a communication link or links with one or more servers, in which each client processing terminal and each server is adapted to provide an object-oriented processing platform and is responsive to the establishment of a connection over a communication link between a client and a server to transmit a multiplex/demultiplex object to the client or server to which it has been connected which object defines a data multiplexor/demultiplexor to be used during such connection.
According to a second aspect of the invention there is provided a method for controlling communication between the components of a distributed data processing system having one or more client processing terminals arranged for communication over a communication link or links with one or more servers, comprising providing each component with an object orientated processing platform and, in response to the establishment of a connection over a communication link between a client and a server, causing each component involved in the connection to transmit a multiplex/demultiplex object to the other component, which object defines a data multiplexor/demultiplexor to be used during such connection.
There is further provided a method of controlling communication between the components of a distributed data processing system comprising providing each component with an object-oriented processing platform, providing for each application involving data transmission a network object defining a multiplexor/demultiplexor for use in connection with such application, and causing each component, on establishment of a connection with another component in said system in order to perform an application, to transmit the network object associated with such application to said other component to permit said other component to establish a multiplexor/demultiplexor appropriate to the application.
Thus each application running in the system is effectively provided with its own dedicated data transmission channel or xe2x80x9cpipexe2x80x9d which provides its own data transmission protocols and the desired degree of security.
In a preferred embodiment of the invention the system provides a generic multiplexor/demultiplexor written in the Java language (Java is a trademark of Sun Microsystems, Inc.). In the preferred system, which provides for transactions initiated or authorised by smart cards, the network objects then run as instances of the multiplexor/demultiplexor, being built into each smart card xe2x80x9cappletxe2x80x9d which requires data transmission.